Semiconductor device, electronic device module and network system

ABSTRACT

A semiconductor device including an image sensor device controlled by an adjusting circuit, and the adjusting circuit configured to transmit a control signal to the image sensor device to be controlled according to a transmission cycle synchronized with a reference clock, the image sensor device includes a first period during which the control signal is allowed to be supplied to the image sensor device to be controlled and a second period during which the supplying of the control signal to the image sensor device to be controlled is not preferable compared to that in the first period, the adjusting circuit is configured to, when a transmission timing of the control signal determined according to the transmission cycle is within the second period, adjust the transmission timing of the control signal so that the control signal will be transmitted in the first period to the image sensor device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 14/928,662, filed on Oct. 30, 2015, which is basedon Japanese patent application No. 2014-262577, filed on Dec. 25, 2014,the disclosure of which is incorporated herein in its entirety byreference.

BACKGROUND

The present disclosure relates to a semiconductor device, and can besuitably used, for example, for a semiconductor device that generates asignal to control a device used in a time-synchronized distributedsystem.

In a distributed system including a plurality of elements (nodes)connected to a network, each of the plurality of nodes operates based onits local clock. In some implementations, in order to accomplishsynchronization of events occurring in the plurality of nodes, forexample, the distributed system may need to time-synchronize theplurality of nodes (i.e., their local clocks). The time synchronizationof the distributed system is accomplished by frequently exchangingmessages (information) among the plurality of nodes in the distributedsystem. Typically, any one of the nodes in the distributed system thatis predetermined or dynamically selected serves as a master clock node.The local clock of the master clock node is called a master clock. Themaster clock node exchanges messages (information) with other nodes(slave clock nodes) in the distributed system and thus each slave clocknode synchronizes its local clock (i.e., slave clock) with the masterclock.

Precision Time Protocol (PTP), which is defined in IEEE Standard 1588,is one of the representative examples of a time synchronization methodof the distributed system. Further, generalized PTP (gPTP) defined inIEEE Standard 802.1AS, which is one of the standards that constituteEthernet Audio/Video Bridging (AVB), is known as a time synchronizationmethod using the PTP. The gPTP defines a time synchronization method inIEEE 802.3 network (i.e., Wired LAN) and IEEE 802.11 network (i.e.,Wireless LAN). In the PTP, the master clock node is called a groundmaster clock and the slave clock node is called a clock slave. In orderto accurately synchronize with the ground master clock, the clock slaveexchanges messages (i.e., Sync, Follow Up, Delay Request, and DelayResponse) with the ground master clock, calculates network delay timebased on the transmission time and the reception time of these messages,and adjusts its local clock using the calculated network delay time.

The distributed system that requires the time synchronization is, forexample, a manufacturing system including an industrial robot and ametrology device therefor, a surveillance system including networkedsurveillance cameras, and an automotive camera system. The automotivecamera system includes a surround view camera system, a bird view camerasystem, and a side view camera system. This automotive camera systemuses a plurality of cameras and processes images taken by the pluralityof cameras to assist parking, detect obstacles and the like.

Japanese Patent Application Publication No. 2005-286453 discloses atechnique for synchronizing in time a plurality of cameras, eachconnected to a network, using a synchronization procedure similar to thePTP.

SUMMARY

As described above, a slave clock node in a distributed system exchangesmessages with a master clock node via a network to synchronize its localclock (i.e., the slave clock) with the master clock. However, thefrequency of a local clock oscillator (e.g., a crystal oscillator)within the slave clock node is naturally different from the frequency ofa local clock oscillator (i.e., the master clock) within the masterclock node due to initial manufacturing tolerances, changes intemperature and pressure, and aging degradation. Further, the networkdelay time varies due to forwarding delay jitter in networking devices(e.g., hubs and switches (bridges) in the IEEE 802.3 network) thatconnects nodes. In order to compensate for a decrease in thesynchronization accuracy due to these unstable factors, the slave clocknode continuously exchanges messages with the master clock node andcorrects a local clock offset according to the results of the exchangeof the messages.

When there is a time difference between the slave clock time and themaster clock time, the offset (positive or negative value) is added tothe slave clock time to cancel the time difference. The slave clock timemay greatly vary due to the processing for adjusting the slave clock.That is, the slave clock time jumps backward when the slave clock timeadvances the master clock time and otherwise the slave clock time jumpsforward.

Such a change in the slave clock time may cause a problem when the slavenode controls a device using the slave clock. In particular, when thedevice to be controlled has timing constraints, the change in the slaveclock time may have an influence on the operation of the device to becontrolled. Assume a case, for example, in which the slave clock nodegenerates a periodic synchronization signal (e.g., pulse signal) to besupplied to the device to be controlled according to the slave clock(local clock) time-synchronized with the master clock. When the slaveclock time changes discontinuously, the phase of (the transmission cycleof) the synchronization signal changes discontinuously according to thechange in the slave clock time, and the change in the phase of (thetransmission cycle of) the synchronization signal may have an influenceon the operation of the device to be controlled.

One example of the device to be controlled having the timing constraintsis an image sensor device equipped with a Complementary Metal OxideSemiconductor (CMOS)/Charge Coupled Device (CCD) image sensor. In oneimplementation, the image sensor device expects the reception of thesynchronization signal of one frame period (e.g., 1/30 seconds) or onefield period (e.g., 1/60 seconds) in order to control a shutter timingof the image sensor, an output of a pixel signal by the image sensor andimage signal processing by an image signal processor (ISP). In thiscase, change in the phase of (the transmission cycle of) thesynchronization signal may cause degradation or lack of the pixel signaland an image generated based on the pixel signal. In the case of anautomotive camera system including a plurality of image sensor devices,if an image taken by one of the image sensor devices is degraded, thesystem may lack information on an obstacle that should be detected.

In the following description, a plurality of embodiments which cancontribute to solution of at least one of problems including theaforementioned problem will be described. It should be noted that theaforementioned problem is merely one of problems that will be solved bythe embodiments disclosed in this specification. Other problems andnovel features will be apparent from the description of thespecification and the accompanying drawings.

In one embodiment, a semiconductor device includes an adjusting circuitthat transmits a control signal to a device to be controlled accordingto a transmission cycle synchronized with a reference clock. The deviceto be controlled has a first period during which the control signal isallowed to be supplied to the device to be controlled and a secondperiod during which the supplying of the control signal to the device tobe controlled is not preferable compared to that in the first period.The adjusting circuit is configured to, when a transmission timing ofthe control signal determined according to the transmission cycle iswithin the second period, adjust the transmission timing of the controlsignal so that the control signal will be transmitted in the firstperiod.

In another embodiment, a semiconductor device is configured to generatea control signal to be supplied to a device to be controlled accordingto a transmission cycle synchronized with a reference clock. Thesemiconductor device further operates as follows when the timing fortransmitting the control signal according to the transmission cycle nolonger meets timing constraints of the device to be controlled due to achange in a phase of the transmission cycle. That is, the semiconductordevice is configured to suppress transmission of the control signal thatdoes not meet the timing constraints and transmit the control signalusing a permissible range of the transmission timing within the timingconstraints.

The above embodiments contribute to the solution of the aforementionedproblem.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, advantages and features will be moreapparent from the following description of certain embodiments taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing a configuration example of a network system(distributed system) according to some embodiments;

FIG. 2 is a Block diagram showing a configuration example of a cameramodule according to some embodiments;

FIG. 3 is a diagram for describing one example of timing constraints ofan image sensor device;

FIG. 4 is a diagram for describing one example of timing constraints ofthe image sensor device;

FIG. 5 is a flowchart showing one example of processing performed by anadjusting circuit according to a first embodiment;

FIG. 6 is a diagram for describing a relation between a synchronizationsignal generated by the adjusting circuit and timing constraints of theimage sensor device according to the first embodiment;

FIG. 7 is a diagram for describing a relation between thesynchronization signal generated by the adjusting circuit and timingconstraints of the image sensor device according to the firstembodiment;

FIG. 8 is a Block diagram showing a configuration example of anadjusting circuit according to a second embodiment;

FIG. 9A is a flowchart showing one example of processing performed bythe adjusting circuit according to the second embodiment;

FIG. 9B is a flowchart showing one example of processing performed bythe adjusting circuit according to the second embodiment;

FIG. 10 is a diagram for describing a relation between a synchronizationsignal generated by an adjusting circuit and timing constraints of animage sensor device according to a third embodiment;

FIG. 11 is a diagram for describing a relation between thesynchronization signal generated by the adjusting circuit and timingconstraints of the image sensor device according to the thirdembodiment;

FIG. 12 is a Block diagram showing a configuration example of theadjusting circuit according to the third embodiment;

FIG. 13A is a flowchart showing one example of processing performed bythe adjusting circuit according to the third embodiment;

FIG. 13B is a flowchart showing one example of processing performed bythe adjusting circuit according to the third embodiment;

FIG. 14 is a Block diagram showing a configuration example of anadjusting circuit according to a fourth embodiment;

FIG. 15A is a flowchart showing one example of processing performed bythe adjusting circuit according to the fourth embodiment; and

FIG. 15B is a flowchart showing one example of processing performed bythe adjusting circuit according to the fourth embodiment.

DETAILED DESCRIPTION

Specific embodiments will be described in detail with reference to thedrawings. The same or corresponding elements are denoted by the samereference symbols throughout the drawings and repeated descriptions willbe omitted as appropriate for the sake of clarification of thedescription.

First Embodiment

FIG. 1 shows a configuration example of a network system (distributedsystem) 1 according to this embodiment. The network system 1 includes aplurality of nodes connected to a network 40. These nodes perform timesynchronization using distributed clock synchronization (e.g., PTP orgPTP). In some implementations, the network system 1 may be anautomotive camera system. In the example shown in FIG. 1, a plurality ofcamera modules 10, a master clock 20, and an Electronic Control Unit(ECU) 30 are connected to the network 40. The master clock 20 operatesas a master clock node for distributed clock synchronization and eachcamera module 10 operates as a slave clock node. Each camera module 10exchanges messages (information, signals and the like) with the masterclock 20 to synchronize its local clock (slave clock) with a local clockof the master clock 20. The master clock 20 may have a radio-controlledclock that receives standard time radio waves to synchronize the localclock of the master clock 20 with accurate reference time (real time) ormay have a radio receiver to synchronize the local clock of the masterclock 20 with a Global Positioning System (GPS) satellite or a mobiletelephone base station.

Local clocks included in the plurality of camera modules 10 synchronizein time with the common master clock 20, the plurality of camera modules10 can capture images according to the common clock. The ECU 30communicates with the camera modules 10 via the network 40, controls thecamera modules 10 to capture images, and receives the captured imagesobtained by the camera modules 10. In some implementations, in order toassist parking, the ECU 30 may process images taken by the cameramodules 10 substantially at the same time, generate a surround viewimage or a bird view image, and then display it on a display 31.Further, in some implementations, the ECU 30 may use images taken by thecamera modules 10 substantially at the same time to detect an obstacle.The ECU 30 is a computer system including at least one processor (e.g.,microprocessor or microcontroller) and, in one implementation, mayinclude one or more Integrated Circuit (IC) chips.

The network 40 may include an IEEE 802.3 network (i.e., Wired LAN), anIEEE 802.11 network (i.e., Wireless LAN), or a combination thereof. Inthese cases, the network 40 may include at least one switch (or hub)that relays Media Access Control (MAC) frames transmitted or received bya plurality of nodes including the camera modules 10, the master clock20, and the ECU 30.

Note that the configuration example shown in FIG. 1 is merely oneexample and may be changed as appropriate. For example, the ECU 30 mayalso communicate with the master clock 20 and synchronize a local clockof the ECU 30 with the local clock of the master clock 20.Alternatively, the master clock 20 may be integrally formed with the ECU30 or, in other words, the hardware and function of the master clock 20may be included in the ECU 30. In one more alternative, the hardware andfunction of the master clock 20 may be included in at least one of thecamera modules 10.

In the following description, the configuration and the operation ofeach camera module 10 will be described in detail. FIG. 2 is a Blockdiagram showing a configuration example of the camera module 10. In theexample shown in FIG. 2, the camera module 10 includes a PHY circuit100, a sensor controller 120, and an image sensor device 140. Forexample, although not shown in FIG. 2, the sensor controller 120 and theimage sensor device 140 are mounted on a mounted substrate (e.g., wiringboard, interposer substrate, and motherboard) and are electricallyconnected to each other via wirings formed on the mounted substrate. ThePHY circuit 100 performs signal processing conforming to a physicallayer (PHY layer) of the network 40 and transmits and receives physicallayer signals to and from the network 40.

The image sensor device 140 includes an image sensor 141 (e.g., CMOSimage sensor or CCD image sensor) and an Image Signal Processor (ISP)142. The ISP 142 controls image capturing by the image sensor 141,receives a pixel signal generated by the image sensor 141, performsdigital signal processing including color correction and white balancecorrection on the pixel signal, and thereby generates an image signal.

The sensor controller 120 is connected to the PHY circuit 100 and isconfigured to communicate with other network nodes including the masterclock 20 and the ECU 30 via the network 40. In order to perform thiscommunication, in the configuration example shown in FIG. 2, the sensorcontroller 120 includes a network interface 121. The network interface121 includes a MAC unit 122 and a network protocol stack 123. The MACunit 122 provides, to the network protocol stack 123, MAC layer (datalink layer) services (i.e., signal processing and control) includingmedia access control, error check, and assembly and disassembly of theMAC frames. The network protocol stack 123 provides services in layers(e.g., network layer and transport layer) higher than the MAC layer. Insome implementations, the network protocol stack 123 may support theInternet Protocol (IP), the Transmission Control Protocol (TCP), and theUser Datagram Protocol (UDP).

The sensor controller 120 is further configured to support thedistributed clock synchronization and generate the local clock (slaveclock) time-synchronized with the master clock 20. In order to performthe distributed clock synchronization, in the configuration exampleshown in FIG. 2, the sensor controller 120 includes a Phase Locked Loop(PLL) 124, a timestamp unit (TSU) 125, a Central Processing Unit (CPU)126, and a memory 127. The CPU 126 controls the PLL 124 to generate alocal clock synchronized with the phase and frequency of the masterclock 20. The TSU 125 receives the local clock generated by the PLL 124and generates local timestamps time-synchronized with the absolute time(real time) of the master clock 20. The CPU 126 controls the TSU 125 toperform an offset correction for aligning its timestamps with timestampsgenerated by the master clock 20.

The CPU 126 loads and executes software (programs) for the distributedclock synchronization (e.g., a PTP or gPTP program module) stored in thememory 127 and thereby controls the PLL 124 and the TSU 125. In someimplementations, the CPU 126 exchanges messages with the master clock 20via the network interface 121, calculates a network delay and the timedifference between the local clock time and the absolute time of themaster clock 20, and controls the PLL 124 and the TSU 125 to correct thetime difference. The memory 127 includes a volatile memory and anon-volatile memory. The volatile memory is, for example, a StaticRandom Access Memory (SRAM), a Dynamic RAM (DRAM), or a combinationthereof. The non-volatile memory is, for example, a mask Read OnlyMemory (MROM), a Programmable ROM (PROM), a flash memory, or anycombination thereof.

Further, the sensor controller 120 is configured to control the imagecapturing by the image sensor device 140 according to the local clocktime (local timestamps generated by the TSU 125) time-synchronized withthe master clock 20. Specifically, the sensor controller 120 supplies asynchronization signal 150 to the image sensor device 140 periodicallywith a transmission cycle according to the local clock time, which istime-synchronized with the master clock 20. In order to achieve thispurpose, the sensor controller 120 includes an adjusting circuit 130.The adjusting circuit 130 includes a control circuit 131 and a signalgenerator 132. The control circuit 131 determines the transmission cycleof the synchronization signal 150 based on the local timestamp suppliedfrom the TSU 125. The signal generator 132 generates the synchronizationsignal 150 according to the timing indicated by the control circuit 131and supplies the synchronization signal 150 to the image sensor device140. The image sensor device 140 controls a shutter timing of the imagesensor 141, output of the pixel signal by the image sensor 141 and theimage signal processing by the ISP 142 according to the periodicsynchronization signal 150. Although the transmission cycle (period) ofthe synchronization signal 150 depends on the image sensor device 140,one frame period (e.g., 1/30 seconds) or one field period (e.g., 1/60seconds) is typically employed as the transmission cycle (period) of thesynchronization signal 150.

Further, the sensor controller 120 is configured to receive the imagesignal that has been generated by the image sensor device 140 andtransmit the received image signal to the ECU 30 via the network 40. Thenetwork interface 121 receives the image signal from the image sensordevice 140 and transmits the received image signal to the ECU 30 via thenetwork 40.

As already described above, in order to keep the time synchronization ofthe slave clock included in the sensor controller 120, it is required tocompensate for a degradation in the synchronization accuracy due tovarious uncertain factors (e.g., manufacturing tolerance of a localclock oscillator (crystal oscillator), frequency drift due totemperature, aging degradation, and delay jitter in a network).Therefore, the sensor controller 120 (CPU 126) continuously exchangesmessages with the master clock 20 and corrects the slave clock time (thePLL 124 and the TSU 125). Specifically, when there is a time differencebetween the slave clock time and the master clock time, the sensorcontroller 120 adds the offset (positive or negative value) to the slaveclock time to cancel the time difference.

However, as already described above, the slave clock time may greatlyvary due to the processing for adjusting the slave clock. Such a changein the slave clock time may cause a problem when the sensor controller120 controls the image sensor device 140 using the slave clock time.Specifically, the phase of (the transmission cycle of) thesynchronization signal 150 also changes discontinuously according to thechange in the slave clock time, and the change in the phase may have aninfluence on the operation of the image sensor device 140. This isbecause, since the image sensor device 140 expects to periodicallyreceive the synchronization signal 150 (e.g., one frame period (e.g.,1/30 seconds) or one field period (e.g., 1/60 seconds)) and controls theimage sensor 141 and the ISP 142 according to the periodicsynchronization signal 150, the change in the phase of (the transmissioncycle of) the synchronization signal 150 may cause degradation or lackof the pixel signal and the image signal generated based on the pixelsignal. In the following description, the influence of the phase changein the synchronization signal 150 on the operation of the image sensordevice 140 will be described, and the operation of the adjusting circuit130 to reduce this influence will also be described.

FIG. 3 is a diagram showing one example of timing constraints imposed onthe image sensor device 140. A transmission cycle 300 shown in FIG. 3shows one example of the transmission cycle of the synchronizationsignal 150 and a synchronization signal waveform 320 shows one exampleof the periodic synchronization signal 150. In the example shown in FIG.3, a period P1 of the transmission cycle 300 is one frame period ( 1/30seconds, i.e., about 33.3 milliseconds) and pulses 302 and 304 indicatetransmission timings of the synchronization signal. The synchronizationsignal waveform 320 according to the transmission cycle 300 is a pulsewave having a period of 1/30 seconds (about 33.3 milliseconds) andincludes pulses 322 and 324.

A state 340 of the image sensor device 140 shown in FIG. 3 indicates thetiming constraints of the image sensor device 140. That is, the state340 includes an acceptable period (342, 346) and an unacceptable period(344) that are alternately repeated. The acceptable period (342, 346)means a period during which the image sensor device 140 can accept thesynchronization signal 150 (i.e., synchronization signal pulses 322 and324 shown in FIG. 3) or, in other words, the image sensor device 140expects to receive the synchronization signal 150. It can also be saidthat the acceptable period (342, 346) is a preferred period for theimage sensor device 140 to normally operate or is a period during whichthe image generated by the image sensor device 140 is not degraded. Asshown in FIG. 3 (362, 364), the image sensor device 140 reads out (oroutputs) the pixel signal from the image sensor 141 upon receiving thesynchronization signal 150 (i.e., synchronization signal pulses 322,324).

On the other hand, the unacceptable period (344) means a period duringwhich it is not preferable to receive the synchronization signal 150(i.e., synchronization signal pulses 322 and 324 in FIG. 3) in the imagesensor device 140. It can be said that the unacceptable period (344) isa period during which it is inappropriate to receive the synchronizationsignal 150, a period during which the normal operation of the imagesensor device 140 is not guaranteed, or a period during which the imagegenerated by the image sensor device 140 is degraded. Although the imagesensor device 140 is able to receive the synchronization signal 150 inthe unacceptable period (344), the pixel signal and the image generatedbased on the pixel signal may be degraded or lost. In someimplementations, the acceptable period (342, 346) corresponds to avertical blanking period in which the pixel signal is read out (oroutput) from each pixel of the image sensor 141 and the unacceptableperiod (344) corresponds to an exposure period (accumulation period) inwhich charge accumulation is performed in each pixel of the image sensor141. In this case, it can be said that the synchronization signal 150specifies a “readout pulse” that indicates timing for reading out thepixel signal.

The timing constraints of the image sensor device 140 include a maximumlength (PA) of the acceptable periods (342, 346) and a predeterminedlength (PB) of the unacceptable period (344). As shown in FIG. 3, theunacceptable period (344) is a fixed period having a predeterminedlength PB (e.g., about 32.3 milliseconds) shorter than the transmissioncycle of the synchronization signal 150 (e.g., one frame period, that isabout 33.3 milliseconds). Now, a difference D (e.g., 1 millisecond)between the transmission cycle length of the synchronization signal 150and the predetermined length of the unacceptable period (344) will bedefined. Meanwhile, the acceptable period (342, 346) is a non-fixedperiod that begins after the unacceptable period (344) and ends uponreceiving the synchronization signal 150 (pulses 322 and 324). Themaximum length PA of the acceptable period (342, 346) is equal to orlonger than the difference D (e.g., 1 millisecond) but equal to orshorter than the length PB of the unacceptable period (344). In oneexample, the maximum length PA of the acceptable period may be twice aslong as the difference D (e.g., 2 milliseconds).

FIG. 4 shows an operation example of the image sensor device 140 whenthe above timing constraints are violated. In the example shown in FIG.4, the phase of the transmission cycle 400 changes due to any factorsuch as adjustment of the slave clock time. Specifically, the phase ofthe transmission cycle 400 changes after a pulse 402 and thus theinterval between the pulse 402 and a pulse 404 becomes shorter than thelength (PB) of the unacceptable period. Note that a pulse 406 shown by adashed line shows a normal transmission timing which would arrive nextto the pulse 402 according to the normal period P1 of the transmissioncycle if the change in the phase of the transmission cycle did notoccur.

A synchronization signal waveform 420 shown in FIG. 4 shows transmissiontimings of the synchronization signal 150 when it is assumed that thetiming adjustment of the synchronization signal 150 by the sensorcontroller 120 (adjusting circuit 130) is not performed. That is, asynchronization signal pulse 422 is generated according to thetransmission timing 402 before the phase change and a synchronizationsignal pulse 424 is generated according to the transmission timing 404after the phase change. When the synchronization signal pulse 424 istransmitted, the image sensor device 140 is still in the unacceptableperiod (444). In one implementation, the image sensor device 140interrupts the unacceptable period (444) and starts a new unacceptableperiod 446, interrupts the readout (or output) of a pixel signal 462,and attempts to output a new pixel signal according to the transmissioncycle after the phase change. However, since the amount of electriccharges accumulated in the pixels of the image sensor 141 is notsufficiently large, a pixel signal output 464 may degrade or lost.

In order to prevent the problem described with reference to FIG. 4, thesensor controller 120 (adjusting circuit 130) according to thisembodiment operates as follows. FIG. 5 is a flowchart showing processing500 that is one example of the processing performed by the adjustingcircuit 130. In Block 501, according to the real time clock (e.g., localtimestamp information supplied from the TSU 125), the control circuit131 in the adjusting circuit 130 detects the transmission timing of thesynchronization signal 150 synchronized with the real time clock. Asalready described above, the transmission cycle of the synchronizationsignal 150 is normally constant. However, when the slave clock (localclock) is corrected to time-synchronize with the master clock 20, thephase of the transmission cycle of the synchronization signal 150 may bechanged.

In Block 502, the control circuit 131 determines whether thetransmission timing of the synchronization signal 150 is within theacceptable period of the image sensor device 140. The determination inBlock 502 may be performed by determining whether the time elapsed sincethe last transmission timing (transmission time of the synchronizationsignal 150) is equal to or longer than the length PB of the unacceptableperiod of the image sensor device 140.

When the detected transmission timing is within the acceptable period ofthe image sensor device 140 (YES in Block 502), the control circuit 131triggers the signal generator 132 to generate the synchronization signal150 according to the detected transmission cycle. Accordingly, thesignal generator 132 transmits the synchronization signal 150 accordingto the detected transmission cycle (Block 503).

On the other hand, when the detected transmission timing is outside theacceptable period of the image sensor device 140 (NO in Block 502), thecontrol circuit 131 adjusts the transmission timing of thesynchronization signal 150 so that the synchronization signal 150 willbe transmitted within the acceptable period of the image sensor device140. As one example, the control circuit may operate as follows. Thecontrol circuit 131 suppresses transmission of the synchronizationsignal 150 outside the acceptable period. Further, the control circuit131 triggers the signal generator 132 to transmit the synchronizationsignal 150 in a vicinity of the beginning of the acceptable period or ina vicinity of the end of the acceptable period based on the maximumlength PA. Accordingly, the signal generator 132 transmits thesynchronization signal 150 in the vicinity of the beginning of theacceptable period or in the vicinity of the end of the acceptable periodregardless of the detected transmission cycle (Block 504).

When the phase of the transmission cycle has been greatly changed, theadjusting circuit 130 can make the phase of the acceptable period of theimage sensor device 140 approach the phase of the transmission cycle ofthe synchronization signal 150 step by step by repeating the processingshown in FIG. 5, especially the processing of Block 504. In other words,the adjusting circuit 130 repeatedly transmits the synchronizationsignal 150 in the acceptable period of the image sensor device 140,thereby making the transmission timing of the synchronization signal 150gradually approach the transmission timing according to the real timeclock (transmission cycle) after the correction. Consequently, the imagesensor device 140 can follow the transmission cycle of thesynchronization signal 150 after the phase change.

In the following description, with reference to FIGS. 6 and 7, specificexamples of the operations of the adjusting circuit 130 when thetransmission cycle phase of the synchronization signal 150 has beenchanged will be described. FIG. 6 shows a case in which the transmissioncycle phase of the synchronization signal 150 has been advanced. Thecase shown in FIG. 6 occurs when, for example, the slave clock timejumps forward by a correction since the slave clock time lags behind themaster clock time. In the example shown in FIG. 6, the phase of atransmission cycle 600 changes after a pulse 602 and thus the intervalbetween the pulse 602 and a pulse 604 is shorter than the length (PB) ofthe unacceptable period. A pulse 606 which is shown by a dashed lineindicates a normal transmission timing which would arrive next to thepulse 602 according to the normal period P1 of the transmission cycle ifthe change in the phase of the transmission cycle did not occur.

A synchronization signal waveform 620 shown in FIG. 6 shows how thetiming adjustment of the synchronization signal 150 is performed by theadjusting circuit 130. That is, the adjusting circuit 130 generates asynchronization signal pulse 622 according to the transmission timing602 before the phase change. The position of the synchronization signalpulse 622 corresponds to an acceptable period 642 in a state 640 of theimage sensor device 140. The image sensor device 140 starts an output ofthe pixel signal (662) in response to the reception of thesynchronization signal pulse 622 and makes a transition to anunacceptable period 644 in which the charge accumulation in the imagesensor 141 is executed.

Next, the adjusting circuit 130 suppresses transmission of asynchronization signal pulse 624 according to the transmission timing604 after the phase change. This is because the transmission timing 604and the synchronization signal pulse 624 based on the transmissiontiming 604 are within the unacceptable period (644) in the state 640 ofthe image sensor device 140. The adjusting circuit 130 promptlytransmits a synchronization signal pulse 626 in a vicinity of thebeginning of an acceptable period 646 that follows the unacceptableperiod 644. The image sensor device 140 starts an output of the pixelsignal (664) in response to the reception of the synchronization signalpulse 626 and makes a transition to an unacceptable period 648 in whichthe charge accumulation in the image sensor 141 is executed.

It should be noted with respect to FIG. 6 that the transmission timingof the synchronization signal pulse 626 goes ahead of the pulse 606shown by the dashed line, which is the normal transmission timing whichwould arrive next to the pulse 602 according to the normal period P1 ofthe transmission cycle if the change in the phase of the transmissioncycle did not occur. Therefore, by repeating the operation shown in FIG.6 by step by step, the phase of the acceptable period after theacceptable period 646 gradually advances and, consequently, the phase ofthe acceptable period can be adjusted to the phase of the transmissioncycle after the phase change.

FIG. 7 shows a case in which the transmission cycle phase of thesynchronization signal 150 is delayed. The case shown in FIG. 7 occurswhen the slave clock time jumps backward due to a correction since theslave clock time advances the master clock time. In the example shown inFIG. 7, the phase of a transmission cycle 700 changes after a pulse 702and thus the interval between the pulse 702 and a pulse 706 is longerthan the sum of the length of the unacceptable period and the maximumlength of an acceptable period 746 (i.e., PB+PA). A pulse 704 shown by adashed line shows the normal transmission timing which would arrive nextto the pulse 702 according to the normal period P1 of the transmissioncycle if the change in the phase of the transmission cycle did notoccur.

A synchronization signal waveform 720 in FIG. 7 shows how the timingadjustment of the synchronization signal 150 is performed by theadjusting circuit 130. That is, the adjusting circuit 130 generates asynchronization signal pulse 722 according to the transmission timing702 before the phase change. The position of the synchronization signalpulse 722 corresponds to an acceptable period 742 in a state 740 of theimage sensor device 140. The image sensor device 140 starts an output ofthe pixel signal (762) in response to the reception of thesynchronization signal pulse 722 and makes a transition to anunacceptable period 744 in which the charge accumulation in the imagesensor 141 is executed.

Next, when the transmission timing does not arrive around thetransmission timing 704 expected base on the last transmission timing702, or in the acceptable period 746, the adjusting circuit 130transmits a synchronization signal pulse 724 in a vicinity of the end ofthe acceptable period 746 determined based on the maximum length PA. Theimage sensor device 140 starts an output of the pixel signal (764) inresponse to the reception of the synchronization signal pulse 724 andmakes a transition to an unacceptable period 748 in which the chargeaccumulation in the image sensor 141 is executed. The adjusting circuit130 suppresses transmission of the synchronization signal pulse 726according to the transmission timing 706 after the phase change. This isbecause the transmission timing 706 and the synchronization signal pulse726 based on the transmission timing 706 are within the unacceptableperiod (748) in the state 740 of the image sensor device 140.

It should be noted with respect to FIG. 7 that the transmission timingof the synchronization signal pulse 724 lags behind the pulse 704 shownby the dashed line, which is the normal transmission timing which wouldarrive next to the pulse 702 according to the normal period P1 of thetransmission cycle if the change in the phase of the transmission cycledid not occur. Therefore, by repeating the operation shown in FIG. 7 bystep by step, the phase of the acceptable period after the acceptableperiod 746 gradually delays and, consequently, the phase of theacceptable period can be matched to the phase of the transmission cycleafter the phase change.

As will be understood from the above description, the adjusting circuit130 is configured to, when the transmission timing of thesynchronization signal 150 determined according to the transmissioncycle does not meet the timing constraints of the image sensor device140, that is, when the transmission timing of the synchronization signal150 is within the unacceptable period of the image sensor device 140,adjust the transmission timing of the synchronization signal 150 so thatthe synchronization signal 150 will be transmitted within the acceptableperiod of the image sensor device 140. In one example, the adjustingcircuit 130 may be configured to suppress transmission of thesynchronization signal 150 that does not meet the timing constraints ofthe image sensor device 140 and to transmit the synchronization signal150 using the permissible range of the transmission timing within thetiming constraints. By repeating this operation, the adjusting circuit130 or the sensor controller 120 including the adjusting circuit 130 cangradually shift the phase of the acceptable period of thesynchronization signal 150 conforming to the timing constraints so thatthe phase of the acceptable period approaches the phase of thetransmission cycle after the phase change. Consequently, the imagesensor device 140 can eventually follow the transmission cycle of thesynchronization signal 150 after the phase change. The adjusting circuit130 and the sensor controller 120 including the adjusting circuit 130can thus follow the phase change of the transmission cycle of thesynchronization signal 150 due to the correction or the like of theslave clock time, while avoiding degradation and lack of the imagegenerated by the image sensor device 140 due to violation of the timingconstraints of the image sensor device 140.

Second Embodiment

In this embodiment, a specific example of the configuration and theoperation of the adjusting circuit 130 described in the first embodimentwill be described. The configuration examples of the network system andthe sensor controller according to this embodiment may be similar tothose shown in FIGS. 1 and 2 described in the first embodiment.

FIG. 8 is a Block diagram showing a configuration example of theadjusting circuit 130. In the example shown in FIG. 8, the adjustingcircuit 130 includes a memory 805, in addition to the control circuit131 and the signal generator 132. The memory 805 includes a volatilememory or a combination of a volatile memory and a non-volatile memory.The memory 805 stores configuration data used by the control circuit 131and the signal generator 132 and also stores data generated by thecontrol circuit 131.

More specifically, the memory 805 stores configuration informationincluding the maximum value PA of the acceptable period of the imagesensor device 140, the predetermined length PB of the unacceptableperiod of the image sensor device 140, and the drive period and thepolarity of the synchronization signal 150. The memory 805 furtherstores an arrival time T1 of the transmission cycle based on the slaveclock time and an immediately previous generation time S0 of thesynchronization signal 150. The arrival time T1 and the generation timeS0 are generated by the control circuit 131. The control circuit 131measures the arrival time T1 and the generation time S0 based on thelocal time in the control circuit 131 generated by a time controller 802that will be described later.

The control circuit 131 shown in FIG. 8 includes a receptiondetermination unit 801, a time controller 802, a timing adjustment unit803, and an ignore flag generation unit 804. In one implementation, thereception determination unit 801 receives from the TSU 125 the localtimestamps indicating the absolute time (real time) synchronized withthe master clock 20 and determines the arrival of the predeterminedtransmission cycle of the synchronization signal 150 based on the localtimestamp. In another implementation, the reception determination unit801 may receive a timing signal indicating the transmission cycle basedon the slave clock time synchronized in time with the master clock timeand determine the arrival of the transmission cycle of thesynchronization signal 150 based on the timing signal. As one example,this timing signal may be a pulse signal such as transmission cyclewaveforms (300, 400, 600 and 700) shown in FIGS. 3, 4, 6 and 7. In thiscase, the TSU 125 or a circuit coupled to the TSU 125 may generate thetiming signal.

The reception determination unit 801 measures the arrival time T1 of thetransmission cycle of the synchronization signal 150 based on the localtime generated by the time controller 802 and stores the measuredarrival time T1 in the memory 805. The operation of the receptiondetermination unit 801 varies according to whether the arrival time T1of the transmission cycle is within the acceptable period of the imagesensor device 140.

The timing adjustment unit 803 and the ignore flag generation unit 804collaborate with the reception determination unit 801 and execute thetransmission timing adjustment of the synchronization signal 150described in the first embodiment. The ignore flag generation unit 804manages the state of an ignore flag (ignore_flg) indicating whether toignore the arrival of the transmission cycle of the synchronizationsignal 150 in the reception determination unit 801.

FIGS. 9A and 9B are flowcharts showing processing 900 that is an exampleof processing performed by the adjusting circuit 130 shown in FIG. 8.Blocks 901 to 905 are executed by the reception determination unit 801.In Block 901, the reception determination unit 801 receives timestampinformation indicating the slave clock synchronized in time with themaster clock 20 or receives the timing signal based on the slave clocktime, and determines the arrival of the transmission cycle of thesynchronization signal 150. As described above, the timing signal may bea pulse signal indicating the transmission timing of the synchronizationsignal 150.

In response to the arrival of the transmission cycle of thesynchronization signal 150 (YES in Block 901), processing of Blocks 902to 906 are executed. Otherwise these processing are skipped. In Block902, the reception determination unit 801 acquires, from the memory 805,the maximum length (PA) of the acceptable period of the image sensordevice 140, the predetermined length (PB) of the unacceptable period ofthe image sensor device 140, and the immediately previous generationtime (S0) of the synchronization signal 150. In Block 903, the receptiondetermination unit 801 determines whether the current local time (T)supplied from the time controller 802 is within the acceptable period ofthe image sensor device 140 (i.e., S0+PB<T<=S0+PB+PA).

When the local time (T) is within the acceptable period (YES in Block903), the reception determination unit 801 stores in the memory 805 thearrival time (T1) of the transmission cycle of the synchronizationsignal 150 based on the local time (T) (Block 905). On the other hand,when the local time (T) is outside the acceptable period (NO in Block903), the reception determination unit 801 checks the state of theignore flag (ignore_flg) (Block 904). When the value of the ignore flagis zero (YES in Block 904), the reception determination unit 801 storesin the memory 805 the arrival time (T1) of the transmission cycle of thesynchronization signal 150 based on the local time (T) (Block 905). Whenthe value of the ignore flag is 1 (NO in Block 904), the receptiondetermination unit 801 does not store in the memory 805 the arrival time(T1) of the transmission cycle of the synchronization signal 150.

Block 906 is executed by the ignore flag generation unit 804. The ignoreflag generation unit 804 sets (clears) the ignore flag to the value zeroin Block 906.

Blocks 907 to 915 except for Block 913 are executed by the timingadjustment unit 803. Block 913 is executed by the ignore flag generationunit 804. In Block 907, the timing adjustment unit 803 acquires, fromthe memory 805, the maximum length (PA) of the acceptable period of theimage sensor device 140, the predetermined length (PB) of theunacceptable period of the image sensor device 140, the immediatelyprevious generation time (S0) of the synchronization signal 150, and thearrival time (T1) of the transmission cycle of the synchronizationsignal 150. In Block 908, the timing adjustment unit 803 determineswhether the current local time (T) supplied from the time controller 802is within the acceptable period of the image sensor device 140 (i.e.,S0+PB<T<=S0+PB+PA). When the local time (T) is not in the acceptableperiod (NO in Block 908), the processing of Block 909 to 916 areskipped, the adjusting circuit 130 updates the local time (T) (Block917), and the processing goes back to Block 901.

On the other hand, when the local time (T) is within the acceptableperiod (YES in Block 908), the timing adjustment unit 803 further checksthe arrival time (T1) of the transmission cycle (Blocks 909 and 910).More specifically, when the arrival time (T1) of the transmission cycleis before the acceptable period of the image sensor device 140 (i.e.,S0<T1<=S0+PB) (YES in Block 909), the timing adjustment unit 803generates a trigger signal (sync_trg) to generate the synchronizationsignal 150 and supplies the trigger signal (sync_trg) to the signalgenerator 132 (Block 914). The timing adjustment unit 803 stores in thememory 805 the generation time (S0) of the trigger signal (sync_trg)based on the local time (T) (Block 915). This corresponds to the case inwhich the phase of the transmission cycle of the synchronization signal150 is advanced, as described with reference to FIG. 6.

When the arrival time (T1) of the transmission cycle is within theacceptable period of the image sensor device 140 (i.e.,S0+PB<T1<=S0+PB+PA) (YES in Block 910), the timing adjustment unit 803supplies the trigger signal (sync_trg) to the signal generator 132 togenerate the synchronization signal 150 (Block 914). The timingadjustment unit 803 stores in the memory 805 the generation time (S0) ofthe trigger signal (sync_trg) based on the local time (T) (Block 915).This corresponds to the case in which the phase of the transmissioncycle of the synchronization signal 150 is normal, as described withreference to FIG. 3.

When neither the determination condition in Block 909 (i.e.,S0<T1<=S0+PB) nor the determination condition in Block 910 (i.e.,S0+PB<T1<=S0+PB+PA) is satisfied and the local time (T) has reached theend (maximum length PA) of the acceptable period of the image sensordevice 140 (i.e., T=S0+PB+PA, YES in Block 911), the timing adjustmentunit 803 generates a delay trigger signal (delay_trg) (Block 912) andalso generates a trigger signal (sync_trg) to generate thesynchronization signal 150 (Block 914). The timing adjustment unit 803stores in the memory 805 the generation time (S0) of the trigger signal(sync_trg) based on the local time (T) (Block 915). This corresponds tothe case in which the phase of the transmission cycle of thesynchronization signal 150 is delayed, as described with reference toFIG. 7. The ignore flag generation unit 804 sets the ignore flag(ignore_flg) to the value 1 in response to receiving the delay triggersignal (delay_trg) (Block 913).

In Block 916, in response to receiving the trigger signal (sync_trg)from the timing adjustment unit 803, the signal generator 132 generatesand supplies the synchronization signal 150 to the image sensor device140. In Block 917, the time controller 802 updates the local time (T).

According to the configuration and the operation of the adjustingcircuit 130 described in this embodiment, it is possible to obtaineffects substantially the same as those in the adjusting circuit 130described in the first embodiment.

Third Embodiment

In this embodiment, another specific example of the configuration andthe operation of the adjusting circuit 130 described in the firstembodiment will be described. The configuration examples of the networksystem and the sensor controller according to this embodiment may besimilar to those shown in FIGS. 1 and 2.

In this embodiment, an improvement of the method for adjusting thetransmission timing of the synchronization signal 150 is provided. Inthe method described in the first and second embodiments, when thetransmission cycle phase of the synchronization signal 150 has beenadvanced, the adjusting circuit 130 repeats the operation oftransmitting the synchronization signal 150 in the vicinity of thebeginning of the acceptable period of the image sensor device 140,thereby gradually advancing the phase of the acceptable period and,consequently, the phase of the acceptable period is adjusted to thetransmission cycle phase of the synchronization signal 150. This methodmay be not efficient, however, when the phase of the transmission cycleof the synchronization signal 150 has been greatly advanced. This isbecause the phase difference at most equal to the predetermined length(PB) of the unacceptable period has to be adjusted. Similarly, thismethod may be not efficient when the phase of the transmission cycle ofthe synchronization signal has been greatly delayed.

In order to address this problem, the method for adjusting thetransmission timing of the synchronization signal 150 according to thisembodiment is executed as follows. That is, when the phase of thetransmission cycle of the synchronization signal 150 is greatly (e.g., ahalf or more of the length PB of the unacceptable period) advanced, theadjusting circuit 130 repeats the operation of transmitting thesynchronization signal 150 in the vicinity of the end, determined basedon the maximum length (PA), of the acceptable period of the image sensordevice 140. That is, in contrast to the operations in the first andsecond embodiments, the phase of the acceptable period is graduallydelayed and, consequently, the phase of the acceptable period iseventually adjusted to the transmission cycle phase of thesynchronization signal 150.

FIG. 10 is a diagram showing one example of the method for adjusting thetransmission timing of the synchronization signal 150 according to thisembodiment. FIG. 10 shows a case in which the transmission cycle phaseof the synchronization signal 150 is advanced by a half or more of thelength PB of the unacceptable period. In the example shown in FIG. 10,the phase of a transmission cycle 1000 changes after a pulse 1002 andthus the interval between the pulse 1002 and a pulse 1004 is a half orless of the length (PB) of the unacceptable period.

A synchronization signal waveform 1020 shown in FIG. 10 shows how thetiming adjustment of the synchronization signal 150 is performed in theadjusting circuit 130. That is, the adjusting circuit 130 generates asynchronization signal pulse 1022 according to the transmission timing1002 before the phase change. The position of the synchronization signalpulse 1022 corresponds to an acceptable period 1042 in a state 1040 ofthe image sensor device 140. The image sensor device 140 starts anoutput of the pixel signal (1062) in response to the reception of thesynchronization signal pulse 1022 and makes a transition to anunacceptable period 1044 where the charge accumulation in the imagesensor 141 is executed.

Next, the adjusting circuit 130 suppresses transmission of asynchronization signal pulse 1024 in response to the transmission timing1004 after the phase change. This is because the transmission timing1004 and the synchronization signal pulse 1024 based on the transmissiontiming 1004 are within an unacceptable period (1044) in the state 1040of the image sensor device 140.

The above description regarding FIG. 10 is similar to the descriptionregarding FIG. 6 according to the first embodiment. However, thefollowing processing of the adjustment method shown in FIG. 10 isdifferent from the adjustment method shown in FIG. 6. That is, theadjustment method shown in FIG. 6 described above includes promptlytransmitting the synchronization signal pulse 626 in the vicinity of thebeginning of the acceptable period 646, which follows the unacceptableperiod 644. Meanwhile, the adjustment method shown in FIG. 10 includestransmitting a synchronization signal pulse 1026 in the vicinity of theend, determined based on the maximum length PA, of an acceptable period1046 following the unacceptable period 1044.

That is, in the method shown in FIG. 10, when the interval from theimmediately previous transmission time (S0) of the synchronizationsignal to the arrival time of the next transmission cycle is shorterthan a half of the length (PB) of the unacceptable period, the adjustingcircuit 130 gradually delays the phase of the acceptable period insteadof gradually advancing the phase of the acceptable period. Accordingly,the phase difference that should be adjusted by the adjusting circuit130 is about a half of the length (PB) of the unacceptable period atmost. Therefore, according to the method shown in FIG. 10, when thetransmission cycle phase of the synchronization signal 150 has beengreatly varied, the transmission cycle phase of the synchronizationsignal 150 can be matched to the phase of the acceptable period of theimage sensor device 130 more promptly.

FIG. 11 is an example when the change of the transmission cycle phase ofthe synchronization signal 150 is small. More specifically, in theexample shown in FIG. 11, the phase of a transmission cycle 1100 ischanged after a pulse 1102 and the interval between the pulse 1102 and apulse 1104 is larger than a half of the length (PB) of the unacceptableperiod but equal to or smaller than PB. Since the operation of the caseshown in FIG. 11 is similar to that of FIG. 6, the detailed descriptionwill be omitted. That is, the transmission cycle 1100, the pulse 1102,and the pulse 1104 shown in FIG. 11 respectively correspond to thetransmission cycle 600, the pulse 602, and the pulse 604 shown in FIG.6. Further, a synchronization signal waveform 1120, a pulse 1122, apulse 1124, and a pulse 1126 shown in FIG. 11 respectively correspond tothe synchronization signal waveform 620, the pulse 622, the pulse 624,and the pulse 626 shown in FIG. 6. Further, a state 1140, an acceptableperiod 1142, an unacceptable period 1144, an acceptable period 1146, anunacceptable period 1148, a pixel signal output 1162, and a pixel signaloutput 1164 of the image sensor device shown in FIG. 11 respectivelycorrespond to the state 640, the acceptable period 642, the unacceptableperiod 644, the acceptable period 646, the unacceptable period 648, thepixel signal output 662, and the pixel signal output 664 shown in FIG.6.

In the following description, a specific example of the configurationsand the operations of the adjusting circuit 130 to execute the timingadjustment method of the synchronization signal 150 described in thisembodiment will be described. FIG. 12 is a Block diagram showing aconfiguration example of the adjusting circuit 130. In the example shownin FIG. 12, the adjusting circuit 130 includes a memory 1205, inaddition to the control circuit 131 and the signal generator 132. Thecontrol circuit 131 shown in FIG. 12 includes a reception determinationunit 1201, a time controller 1202, and a timing adjustment unit 1203. Aswill be clear from the comparison between FIG. 8 and FIG. 12, the ignoreflag generation unit 804 is omitted in the configuration example shownin FIG. 12. In order to execute the timing adjustment method of thesynchronization signal 150 described in this embodiment, the operationsof the reception determination unit 1201 and the timing adjustment unit1203 are different from those of the reception determination unit 801and the timing adjustment unit 803 shown in FIG. 8. The operation of thetime controller 1202 may be similar to that of the time controller 802.

FIGS. 13A and 13B are flowcharts showing processing 1300 that is oneexample of processing performed by the adjusting circuit 130 shown inFIG. 12. Blocks 1301 to 1304 are executed by the reception determinationunit 1201. The processing of Block 1301 may be similar to the processingof Block 901 shown in FIG. 9A.

In response to the arrival of the transmission cycle of thesynchronization signal 150 (YES in Block 1301), processing of Blocks1302 to 1304 are executed. Otherwise, these processing are skipped. InBlock 1302, the reception determination unit 1201 acquires, from thememory 1205, the predetermined length (PB) of the unacceptable period ofthe image sensor device 140 and the immediately previous generation time(S0) of the synchronization signal 150. In Block 1303, the receptiondetermination unit 1201 determines whether the current local time (T)supplied from the time controller 1202 is within the former part of theunacceptable period of the image sensor device 140 (i.e.,S0<T<=S0+PB/2).

When the local time (T) is not within the former part of theunacceptable period (NO in Block 1303), the reception determination unit1201 stores in the memory 1205 the arrival time (T1) of the transmissioncycle of the synchronization signal 150 based on the local time (T)(Block 1304). On the other hand, when the local time (T) is within theformer part of the unacceptable period (YES in Block 1303), thereception determination unit 1201 does not store in the memory 1205 thearrival time (T1) of the transmission cycle of the synchronizationsignal 150.

Blocks 1305 to 1311 are executed by the timing adjustment unit 1203. Theprocessing of Blocks 1305 and 1306 may be similar to the processing ofBlocks 907 and 908 shown in FIG. 9B. When the local time (T) is notwithin the acceptable period (NO in Block 1306), the processing ofBlocks 1307 to 1311 are skipped, the adjusting circuit 130 updates thelocal time (T) (Block 1313), and the processing goes back to Block 1301.

On the other hand, when the local time (T) is within the acceptableperiod (YES in Block 1306), the timing adjustment unit 1203 furtherchecks the arrival time (T1) of the transmission cycle (Blocks 1307 and1308). Specifically, when the arrival time (T1) of the transmissioncycle is within the latter part (i.e., S0+PB/2<T1<=S0+PB) of theunacceptable period of the image sensor device 140 (YES in Block 1307),the timing adjustment unit 1203 generates the trigger signal (sync_trg)and supplies the trigger signal (sync_trg) to the signal generator 132to generate the synchronization signal 150 (Block 1310). The timingadjustment unit 1203 stores in the memory 1205 the generation time (S0)of the trigger signal (sync_trg) based on the local time (T) (Block1311). This corresponds to the case described with reference to FIG. 11.

When the arrival time (T1) of the transmission cycle is within theacceptable period of the image sensor device 140 (i.e.,S0+PB<T1<=S0+PB+PA) (YES in Block 1308), the timing adjustment unit 1203supplies the trigger signal (sync_trg) to the signal generator 132 togenerate the synchronization signal 150 (Block 1310). The timingadjustment unit 1203 stores in the memory 1205 the generation time (S0)of the trigger signal (sync_trg) based on the local time (T) (Block1311). This corresponds to the case in which the phase of thetransmission cycle of the synchronization signal 150 is normal, asdescribed with reference to FIG. 3.

When neither the determination condition in Block 1307 (i.e.,S0+PB/2<T1<=S0+PB) nor the determination condition in Block 1308 (i.e.,S0+PB<T1<=S0+PB+PA) is satisfied and the local time (T) has reached theend (maximum length PA) of the acceptable period of the image sensordevice 140 (i.e., T=S0+PB+PA, YES in Block 1309), the timing adjustmentunit 1203 supplies the trigger signal (sync_trg) to the signal generator132 to generate the synchronization signal 150 (Block 1310). The timingadjustment unit 1203 stores in the memory 1205 the generation time (S0)of the trigger signal (sync_trg) based on the local time (T) (Block1311). This corresponds to the case in which the phase of thetransmission cycle of the synchronization signal 150 is delayed, asdescribed with reference to FIG. 7, and the case in which thetransmission cycle phase has been greatly advanced, as described withreference to FIG. 10.

The processing of Blocks 1312 and 1313 may be similar to the processingof Blocks 916 and 917 shown in FIG. 9B.

Fourth Embodiment

In this embodiment, modification of the configuration and the operationof the adjusting circuit 130 described in the third embodiment will bedescribed. The configuration examples of the network system and thesensor controller according to this embodiment may be similar to thoseshown in FIGS. 1 and 2 described in the first embodiment.

FIG. 14 is a Block diagram showing a configuration example of theadjusting circuit 130. In the example shown in FIG. 14, the adjustingcircuit 130 includes a memory 1405, in addition to the control circuit131 and the signal generator 132. The control circuit 131 shown in FIG.14 includes a reception determination unit 1401, a counter controller1402, and a timing adjustment unit 1403. As will be clear from thecomparison between FIG. 12 and FIG. 14, in the configuration exampleshown in FIG. 14, the time controller 1202 is replaced by the countercontroller 1402. In accordance therewith, the timing adjustment unit1403 needs not store the generation time (S0) of the synchronizationsignal 150 in the memory 1405. Further, the reception determination unit1401 supplies the synchronization flag (sync_flg) indicating the arrivalof the transmission cycle to the timing adjustment unit 1403, therebyeliminating the need to store the arrival time (T1) of the transmissioncycle of the synchronization signal 150 in the memory 1405.

According to the configuration example shown in FIG. 14, there is noneed to store the immediately previous generation time (S0) of thesynchronization signal 150 and the arrival time (T1) of the transmissioncycle in the memory 1405. Accordingly, the size of the circuit can bereduced compared to that in the configuration example shown in FIG. 12described in the third embodiment.

FIGS. 15A and 15B show a flowchart showing processing 1500 that is oneexample of processing performed by the adjusting circuit 130 shown inFIG. 14. The processing of Block 1501 may be similar to the processingof Block 901 shown in FIG. 9A or the processing of Block 1301 shown inFIG. 13A.

The processing of Blocks 1502 to 1504 is substantially the same as theprocessing of Blocks 1302 to 1304 except for some changes therein due tothe employment of the counter controller 1402. That is, in response tothe arrival of the transmission cycle of the synchronization signal 150(YES in Block 1501), the processing of Blocks 1502 to 1504 are executed,and otherwise this processing is skipped. In the Block 1502, thereception determination unit 1401 acquires the predetermined length (PB)of the unacceptable period of the image sensor device 140 from thememory 1405. In Block 1503, the reception determination unit 1401determines whether the counter value (T) corresponding to the currentlocal time supplied from the counter controller 1402 is within theformer part of the unacceptable period of the image sensor device 140(i.e., 0<T<=PB/2).

When the counter value (T) is not within the former part of theunacceptable period (NO in Block 1503), the reception determination unit1401 sets the synchronization flag (sync_flg) to the value 1 to notifythe timing adjustment unit 1403 of the arrival of the transmission cycleof the synchronization signal 150 (Block 1504). On the other hand, whenthe counter value (T) is within the former part of the unacceptableperiod (YES in Block 1503), the reception determination unit 1401 doesnot set the synchronization flag (sync_flg).

Blocks 1505 to 1509 are executed by the timing adjustment unit 1403. InBlock 1505, the timing adjustment unit 1403 acquires, from the memory1405, the predetermined length (PB) of the unacceptable period and themaximum length (PA) of the acceptable period of the image sensor device140. In Block 1506, the timing adjustment unit 1403 determines whetherthe current counter value (T) supplied from the counter controller 1402is within the acceptable period of the image sensor device 140 (i.e.,PB<T<=PB+PA). When the counter value (T) is not within the acceptableperiod (NO in Block 1506), the processing of Blocks 1507 to 1511 areskipped, the adjusting circuit 130 updates the counter value (T) (i.e.,local time) by incrementing the counter in the counter controller 1402(Block 1513), and the processing goes back to Block 1501.

On the other hand, when the counter value (T) is within the acceptableperiod (YES in Block 1506), the timing adjustment unit 1403 furtherchecks the value of the synchronization flag (sync_flg). Specifically,when the value of the synchronization flag (sync_flg) is 1 (YES in Block1507), the timing adjustment unit 1403 generates a trigger signal(sync_trg) and supplies the trigger signal (sync_trg) to the signalgenerator 132 to generate the synchronization signal 150 (Block 1509).That the value of the synchronization flag (sync_flg) is 1 correspondsto the case in which the arrival time (T1) of the transmission cycle iswithin the latter part of the unacceptable period of the image sensordevice 140 (i.e., S0+PB/2<T1<=S0+PB) or the case in which the arrivaltime (T1) of the transmission cycle is within the acceptable period(i.e., S0+PB<T1<=S0+PB+PA). Therefore, this corresponds to the casedescribed with reference to FIG. 11 or the case described with referenceto FIG. 3.

When the value of the synchronization flag (sync_flg) is 0 (NO in Block1507) and the counter value (T) has reached the end (maximum length PA)of the acceptable period of the image sensor device 140 (i.e., T=PB+PA,YES in Block 1508), the timing adjustment unit 1403 supplies the triggersignal (sync_trg) to the signal generator 132 to generate thesynchronization signal 150 (Block 1509). This corresponds to the case inwhich the phase of the transmission cycle of the synchronization signal150 has been delayed, as described with reference to FIG. 7, and thetransmission cycle phase has been greatly advanced, as described withreference to FIG. 10.

The synchronization flag (sync_flg) is set (cleared) to the value zeroafter the trigger signal (sync_trg) has been generated. The processingof Block 1511 may be similar to the processing of Block 916 shown inFIG. 9B or the processing of Block 1312 shown in FIG. 13B. In Block1512, upon generating the synchronization signal 1511, the countercontroller 1402 sets (resets) the counter that measures the local timeto the value zero.

In the configurations and the operations described with reference toFIGS. 14, 15A and 15B, the counter controller 1402 operates to countfrom 0 to PB+PA. In one implementation, a state signal that indicatesthe acceptable period and the unacceptable period of the image sensordevice 140 may be newly provided and the counter controller 1402 maycount the acceptable period from 0 to PA and the unacceptable periodfrom 0 to PB. In this case, in Block 1503 shown in FIG. 15A, besidesdetermining whether the counter value (T) is 0<T<=PB/2, the receptiondetermination unit 1401 may further determine whether the state signalindicates the unacceptable period. On the other hand, in Block 1506 inFIG. 15B, the timing adjustment unit 1403 may only determine whether thestate signal indicates the acceptable period. Further, in Block 1508 inFIG. 15B, the timing adjustment unit 1403 may determine whether thecounter value (T) is PA (T=PA) and the state signal indicates theacceptable period. It is therefore possible to eliminate an adder(PB+PA) to calculate the sum of PB and PA in the timing adjustment unit1403.

Other Embodiments

The processing of the control circuit 131 described in the aboveembodiments may be achieved by causing a computer system including atleast one processor to execute a program. More specifically, one or moreprograms including instructions to cause a computer system to executethe algorithm described in the specification using the drawingsincluding the flowcharts may be created and this program(s) may besupplied to the computer system. The program(s) can be stored andprovided to a computer using any type of non-transitory computerreadable media. Non-transitory computer readable media include any typeof tangible storage media. Examples of non-transitory computer readablemedia include magnetic storage media (such as flexible disks, magnetictapes, hard disk drives, etc.), optical magnetic storage media (e.g.,magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R,CD-R/W, and semiconductor memories (such as mask ROM, Programmable ROM(PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM),etc.). The program may be provided to a computer using any type oftransitory computer readable media. Examples of transitory computerreadable media include electric signals, optical signals, andelectromagnetic waves. Transitory computer readable media can providethe program to a computer via a wired communication line (e.g., electricwires, and optical fibers) or a wireless communication line.

In the above embodiments, cases in which the device to be controlled isan image sensor device have been mainly described. However, thetechnical idea described in the above embodiments may be widely used tocontrol a device to be controlled having timing constraints other thanthe image sensor device.

The above-described embodiments can be combined as appropriate ordesirable by one of ordinary skill in the art.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention can bepracticed with various modifications within the spirit and scope of theappended claims and the invention is not limited to the examplesdescribed above.

Further, the scope of the claims is not limited by the embodimentsdescribed above.

Furthermore, it is noted that, Applicant's intent is to encompassequivalents of all claim elements, even if amended later duringprosecution.

What is claimed is:
 1. A semiconductor device comprising: an imagesensor device controlled by an adjusting circuit; and the adjustingcircuit configured to transmit a control signal to the image sensordevice to be controlled according to a transmission cycle synchronizedwith a reference clock, wherein the image sensor device includes a firstperiod during which the control signal is allowed to be supplied to theimage sensor device to be controlled and a second period during whichthe supplying of the control signal to the image sensor device to becontrolled is not preferable compared to that in the first period, theadjusting circuit is configured to, when a transmission timing of thecontrol signal determined according to the transmission cycle is withinthe second period, adjust the transmission timing of the control signalso that the control signal will be transmitted in the first period tothe image sensor device, and the adjusting circuit is further configuredto receive a local timestamp indicating the reference clock and todetermine the transmission cycle based on the local timestamp.
 2. Thesemiconductor device according to claim 1, wherein the first period andthe second period are alternately repeated in the image sensor device,the first period is a non-fixed period that ends upon receiving thecontrol signal, the second period is a fixed period having apredetermined length, the predetermined length of the second period isless than the period of the transmission cycle by a first length, amaximum length of the first period is equal to or greater than the firstlength and less than the predetermined length of the second period, andwhile the transmission timing of the control signal determined accordingto the transmission cycle is not within the first period, the adjustingcircuit repeatedly suppresses transmission of the control signal notwithin the first period and also repeatedly transmits the control signalin a vicinity of a beginning of the first period or in a vicinity of anend of the first period based on the maximum length thereof, therebygradually shifting a phase of the first period so that the phase of thefirst period approaches a phase of the transmission cycle.
 3. Thesemiconductor device according to claim 2, wherein when the transmissiontiming of the control signal determined according to the transmissioncycle arrives before the first period, the adjusting circuit suppressestransmission of the control signal not within the first period andtransmits the control signal in the vicinity of the beginning of thefirst period.
 4. The semiconductor device according to claim 2, whereinwhen the transmission timing of the control signal determined accordingto the transmission cycle arrives after the first period, the adjustingcircuit transmits the control signal in the vicinity of the end of thefirst period based on the maximum length thereof and suppressestransmission of the control signal outside the first period.
 5. Thesemiconductor device according to claim 2, wherein the vicinity of thebeginning of the first period is defined so that a time from a beginningof the second period, which is immediately preceding the first period,to the vicinity of the beginning of the first period becomes less theperiod of the transmission cycle, and the vicinity of the end of thefirst period is defined so that a time from the beginning of the secondperiod, which is immediately preceding the first period, to the vicinityof the end of the first period becomes greater than the period of thetransmission cycle.
 6. The semiconductor device according to claim 1,wherein while the transmission timing of the control signal determinedaccording to the transmission cycle is not within a first period, theadjusting circuit repeatedly suppresses transmission of the controlsignal not within the first period and also repeatedly transmits thecontrol signal in a vicinity of a beginning of the first period or in avicinity of an end of the first period based on a maximum lengththereof, thereby gradually shifting a phase of the first period suchthat the phase of the first period approaches a phase of thetransmission cycle.
 7. A semiconductor device comprising: an imagesensor device; and an adjusting circuit controlling the image sensordevice, wherein the image sensor device includes a first period duringwhich the control signal is allowed to be supplied to the image sensordevice to be controlled and a second period during which the supplyingof the control signal to the image sensor device to be controlled is notpreferable compared to that in the first period, the adjusting circuitis configured to transmit a control signal to the image sensor device tobe controlled according to a transmission cycle synchronized with areference clock, and the adjusting circuit is configured to, when atransmission timing of the control signal determined according to thetransmission cycle is within the second period, adjust the transmissiontiming of the control signal such that the control signal will betransmitted in the first period to the image sensor device.
 8. Thesemiconductor device according to claim 7, wherein the adjusting circuitis further configured to receive a local timestamp indicating thereference clock and to determine the transmission cycle based on thelocal timestamp.
 9. The semiconductor device according to claim 7,wherein the image sensor device includes the first period during whichthe control signal is allowed to be supplied to the image sensor deviceto be controlled and the second period.
 10. The semiconductor deviceaccording to claim 7, wherein the first period and the second period arealternately repeated in the image sensor device, the first period is anon-fixed period that ends upon receiving the control signal, the secondperiod is a fixed period having a predetermined length, thepredetermined length of the second period is less than the period of thetransmission cycle by a first length, and a maximum length of the firstperiod is equal to or greater than the first length and less than thepredetermined length of the second period.
 11. The semiconductor deviceaccording to claim 7, wherein while the transmission timing of thecontrol signal determined according to the transmission cycle is notwithin the first period, the adjusting circuit repeatedly suppressestransmission of the control signal not within the first period and alsorepeatedly transmits the control signal in a vicinity of a beginning ofthe first period or in a vicinity of an end of the first period based ona maximum length thereof, thereby gradually shifting a phase of thefirst period so that the phase of the first period approaches a phase ofthe transmission cycle.
 12. The semiconductor device according to claim11, wherein when the transmission timing of the control signaldetermined according to the transmission cycle arrives before the firstperiod, the adjusting circuit suppresses transmission of the controlsignal not within the first period and transmits the control signal inthe vicinity of the beginning of the first period.
 13. The semiconductordevice according to claim 11, wherein when the transmission timing ofthe control signal determined according to the transmission cyclearrives after the first period, the adjusting circuit transmits thecontrol signal in the vicinity of the end of the first period based onthe maximum length thereof and suppresses transmission of the controlsignal outside the first period.
 14. The semiconductor device accordingto claim 11, wherein the vicinity of the beginning of the first periodis defined so that a time from a beginning of the second period, whichis immediately preceding the first period, to the vicinity of thebeginning of the first period becomes less the period of thetransmission cycle, and the vicinity of the end of the first period isdefined so that a time from the beginning of the second period, which isimmediately preceding the first period, to the vicinity of the end ofthe first period becomes greater than the period of the transmissioncycle.
 15. An adjusting circuit, comprising: a control circuitdetermines a transmission cycle of a synchronization signal; and asignal generator generates the synchronization signal according to atiming indicated by the control circuit and supplies the synchronizationsignal to an image sensor device to be controlled, wherein the controlcircuit and the signal generator are configured to transmit thesynchronization signal to the image sensor device to be controlledaccording to the transmission cycle that is synchronized with areference clock, and the control circuit is configured to, when atransmission timing of the synchronization signal determined accordingto the transmission cycle is within a second period, adjust thetransmission timing of the synchronization signal such that thesynchronization signal will be transmitted in a first period to theimage sensor device.
 16. The adjusting circuit according to claim 15,wherein the control circuit is further configured to receive a localtimestamp indicating the reference clock and to determine thetransmission cycle based on the local timestamp.
 17. The adjustingcircuit according to claim 15, wherein the first period and the secondperiod are alternately repeated in the image sensor device, the firstperiod is a non-fixed period that ends upon receiving a control signal,the second period is a fixed period having a predetermined length, thepredetermined length of the second period is less than the period of thetransmission cycle by a first length, a maximum length of the firstperiod is equal to or greater than the first length and less than thepredetermined length of the second period, and while the transmissiontiming of the control signal determined according to the transmissioncycle is not within the first period, the adjusting circuit repeatedlysuppresses transmission of the control signal not within the firstperiod and also repeatedly transmits the control signal in a vicinity ofa beginning of the first period or in a vicinity of an end of the firstperiod based on the maximum length thereof, thereby gradually shifting aphase of the first period so that the phase of the first periodapproaches a phase of the transmission cycle.
 18. The adjusting circuitaccording to claim 17, wherein when the transmission timing of thecontrol signal determined according to the transmission cycle arrivesbefore the first period, the adjusting circuit suppresses transmissionof the control signal not within the first period and transmits thecontrol signal in the vicinity of the beginning of the first period. 19.The adjusting circuit according to claim 17, wherein when thetransmission timing of the control signal determined according to thetransmission cycle arrives after the first period, the adjusting circuittransmits the control signal in the vicinity of the end of the firstperiod based on the maximum length thereof and suppresses transmissionof the control signal outside the first period.
 20. The adjustingcircuit according to claim 17, wherein the vicinity of the beginning ofthe first period is defined so that a time from a beginning of thesecond period, which is immediately preceding the first period, to thevicinity of the beginning of the first period becomes less the period ofthe transmission cycle, and the vicinity of the end of the first periodis defined so that a time from the beginning of the second period, whichis immediately preceding the first period, to the vicinity of the end ofthe first period becomes greater than the period of the transmissioncycle.